The following discussion of the prior art is provided to place the invention in an appropriate technical context and enable the advantages of it to be more fully understood. It should be appreciated, however, that any discussion of the prior art throughout the specification should not be considered as an express or implied admission that such prior art is widely known or forms part of common general knowledge in the field.
As energy costs rapidly rise, society is desperately searching for ways to reduce greenhouse gas emissions. Solar energy has become one of the most widely employed of the options being considered as an alternative energy source. A solar cell (also called photovoltaic cell or photoelectric cell) is a solid state electrical device that converts the energy of light directly into electricity by the photovoltaic effect. Assemblies of cells are used to make solar modules which are used to capture energy from sunlight, and which are commonly known as solar panels.
Interest in solar energy technology is rapidly on the rise, with many government bodies and industry pouring millions of dollars each year into conducting research into ever more efficient cells. It has been estimated that photovoltaic cell production has been doubling every two years and is the world's fastest growing energy technology. It is also estimated that about 2% of Australian homes have solar panel systems installed, which is forecast to rise substantially over the coming decades. Other countries have already adopted the technology to a greater degree, with some countries having solar panel systems installed on more than 5% of dwellings. Solar technology is not just applicable to urban buildings; it also finds particular utility in commercial, remote or rural applications where it is difficult or costly to connect mains power and, due to advances in efficiency, in commercial and industrial applications.
Solar panels installed on the roof of a building absorb sunlight during the day and instantly convert it into direct current (DC) electrical energy. The electricity is then run into an inverter that converts the DC power into standard alternating current (AC) for use in the home. This electricity is synchronized with the utility power whenever the solar grid is producing electricity, and the electrical panel distributes the solar energy and utility power throughout the home. In some instances it is not uncommon during peak sunlight hours for the utility meter to spin backwards when the solar electricity generated exceeds the home's needs. In this case, the excess power can be sold back to the utility company for a credit. Utility power is automatically provided at night and during times when the home's demand exceeds the solar production. Some systems also include batteries that store electrical energy for use when the sun is not shining.
There are issues, however, associated with solar panel systems, and in particular the safety challenges they present to fire fighters and emergency workers. For example, in 2002 a fire fighter in Switzerland was injured as the result of an electrical shock he received from a solar panel, and in 2007 a fire fighter in Arizona received an indirect electrical shock while fighting a house fire. In this case, the home electricity was secured at the utility box, however the fire fighters operating at this incident were unaware that the solar panel system was still energized. Accordingly, fire fighters and emergency workers are now almost universally trained that when conducting fire ground operations on a building with a solar panel system, the solar panel system must be assumed to be still energized at all times. In other words, even if a building's electrical utilities are shut down at the panel, everything electrically downstream of the utility box must be assumed to be still energized. Whilst it is known that environmental factors can affect a solar panel system's performance, e.g. cloud cover, smog, and temperature, fire fighters and emergency workers are nevertheless trained to always treat the system as if it were energized electrical equipment.
In an attempt to circumvent this problem, some fire fighters have attempted to black out the solar panel system by using a salvage cover to block out the sunlight. In these cases the energy created by the system can be reduced, but this solution does not completely block out the sun, and the system can still produce enough electricity to shock a potential victim. This also means that a fire fighter and emergency worker has to climb onto the roof and install the cover, which presents its own dangers. Furthermore, in high wind conditions it is not uncommon for the cover to be blown off, or even inadvertently removed or partially displaced by the high powered jet of water from the fire fighting equipment.
In another solution, some fire fighters have attempted to cover solar panels with standard fire fighting foam to block out the sunlight, however it has been found that this provided a similar result, namely, sunlight was still able to penetrate through the foam and the solar panel system continued to create electrical energy. In this particular example, it was found that the foam had a tendency to slide off the panels.
There are other electrical dangers which solar panels present. For example, if a fire fighter or and emergency worker were to break the glass protecting a solar cell, this could potentially discharge all of the inherent energy in the system, which could be deadly. Further, fire fighters and emergency workers must be extremely cautious when entering an attic or a roof cavity of a structure with a solar cell system on the roof as exposed wires can fill through the roof into the cavity and shock rescue personnel.
Other dangers relate to the solar cells themselves, which include the use of many hazardous chemicals. To explain, during fire or an explosion a solar cell can release these hazardous chemicals and present an inhalation hazard to fire fighter and emergency workers working around them and any civilians which are downwind. In the case of a small residential system, the exposure hazard is relatively small. Larger arrays like those found on some commercial buildings, however, are more likely to be an exposure hazard for fire fighter and emergency workers and the public.
Once a fire has been extinguished, a solar panel continues to present a real danger to those who are employed to clean up the site. Even if the structure has collapsed and the solar panel is buried underneath rubble it is still possible for the panel to produce an electrical current. Other issues can be caused during flooding. For example, if the mains power switchboard is underneath the water line and the roof structure remains above the waterline the panels will still be able to generate electrical power.
One other problem which solar panels present, is that the “hot stick” many fire departments carry on their engines and ladders detects only alternating current, and using a hot stick to determine if a solar panel system is energized will mislead fire fighters into a false sense of security because everything between the solar cells and the inverter is direct current. Although there may be no current, the wires from the array will have a voltage potential that cannot be detected through non contact means.
It will also be understood that the safety of the fire fighter is paramount, and typically modern fire fighting units engage in “dynamic risk assessment”, which commences from when the fire fighters depart the station. In other words, information on the fire itself the type of the building on fire, its potential contents, and even information on the surrounding buildings is fed back to the fire fighters before and whilst in transit to the fire. In this way, they can arrive at the fire fully informed and are therefore able to make quick and educated decisions. The fire fighters will not commence operations, however, until the risks have been identified and minimised, and in cases where there are solar panels present valuable time can be wasted in rendering the panels safe by conventional methods. Life and property can be put at risk due to this delay.
It is an object of the present invention to overcome or ameliorate one or more of the disadvantages of the prior art, or at least to provide a useful alternative.